This application is based on application No. 11-11607 filed in Japan, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to a camera, and particularly to the camera in which zooming operation and focusing operation are performed with one single driving mechanism.
2. Description of the Related Art
As a construction for realizing miniaturization and cost down of a zoom lens barrel, there has conventionally been known a single driving mechanism for both zooming and focusing operations. In general, in the zoom lens barrel utilizing a first lens group and a second lens group, the focusing operation is performed with the first lens group (namely, the first component) which locates on front side. In the single driving mechanism for both zooming and focusing operations, each lens group moves along one zooming line in which zooming sections and focusing sections are alternately repeated. Therefore, the first lens group moves always linearly to a rotational angle of a cam barrel. This example will be explained below with reference to FIGS. 1A and 1B.
FIGS. 1A and 1B show one example of a zooming line diagram of a two-component zoom lens barrel which performs the focusing operation with the first lens group (first component). This zoom lens barrel, like the embodiments of the present invention described later, comprises a fixed barrel which is immobilized to a camera body, a cam barrel (rotatable barrel) which advances or retreats relative to the fixed barrel, and a first lens group and a second lens group each of which advances or retreats relative to the cam barrel.
In FIG. 1A, a straight line 1 represents a forwarding lead of the cam barrel relative to the fixed barrel, a straight line 3 represents a forwarding lead of the first lens group (first component) relative to the cam barrel, and a stepped line 2 represents a forwarding lead of the second lens group (second component) relative to the cam barrel. Therefore, a forwarding amount of the first lens group relative to the fixed barrel is represented by a sum of the straight lines 1 and 3, which is represented by a straight line 13 in FIG. 1B. Likewise, a forwarding amount of the second lens group relative to the fixed barrel is represented by a sum of the straight line 1 and the stepped line 2, which is represented by a stepped line 12 in FIG. 1B.
This zoom lens barrel performs a stepped zooming operation including six steps in total, which are: telephoto step xe2x80x9cTxe2x80x9d, wideangle step xe2x80x9cWxe2x80x9d and four steps xe2x80x9cM1xe2x80x9d to xe2x80x9cM4xe2x80x9d therebetween. The focusing operation is performed in a plurality of areas corresponding to horizontal sections (focusing sections) of the stepped line 12, and the zooming operation is performed in areas corresponding to other sections (zooming sections) of the stepped line 12. Thus, in the single driving mechanism for both zooming and focusing operations, each lens group moves along one zooming line in which zooming sections and focusing sections are alternately repeated.
As to a curved line 2xe2x80x2 in FIG. 1A, it represents a forwarding lead of the second lens group (second component) relative to the cam barrel in the case of continuous zooming operation, but not the stepped zooming operation. A forwarding amount of the second lens group relative to the fixed barrel is, therefore, represented by a curved line 12xe2x80x2 in FIG. 1B. In such a continuous zooming operation, the focusing operation at each zoomed point is performed by changing, with using another driving mechanism, a relative distance between the first and the second lens groups.
As shown in FIG. 1B, although the second component moves along the stepped zooming line 12, the first component moves always linearly along the zooming line 13. There have existed the following problems in such a conventional zooming/focusing lens barrel wherein one component moves along one straight line over the whole zooming area. A focal length and a view angle change generally according to the positional change of a variator lens, or according to the positional change of the second lens group in the case of the two-component zooming. On the other hand, in the single driving mechanism for both zooming and focusing operations, it is required that, during the focusing operation, a compensator lens, or focusing lens, or the first lens group in the case of the two-component zooming is moved linearly relative to a rotational angle of the lens barrel. Therefore, conventionally, during the zooming operation, the compensator lens is driven with the same lead as that used during the focusing operation, as shown in FIGS. 1A and 1B. That is, the compensator lens is driven with a constant lead over the whole zooming area. The movement of the variator lens for achieving the zooming operation is determined in compliance with the behavior (or movement) of the compensator lens. That is, as shown in FIGS. 1A and 1B, the behavior of the variator lens is determined in accordance with the lead, of the compensator lens, which is linear (namely, constant) over the whole zooming area, out of relation to an ideal focal length and a view angle. Generally, in the case of two-component zooming, the variator lens rapidly moves on a wideangle side, and gently moves on a telephoto side. The focal length and the view angle also changes in accordance therewith. That is, a user, who performs the zooming operation while looking through a view finder, feels that the focal length and the view angle change rapidly on the wideangle side and gently on the telephoto side. Thus, the user who operates the camera has a sense of incongruity or unnaturalness.
Therefore, it is an object of the present invention to provide a camera having a zoom lens barrel which is of a type of employing a single drive mechanism for performing both zooming and focusing operations, in which the variator lens is driven to move so as to realize an ideal change in focal length and view angle while the compensator lens (namely, the focusing lens) is being driven to move linearly with respect to the rotational angle of the lens barrel during the focusing operation, and in which a changing rate of the focal length and the view angle over the whole zooming area is constant to the user of the camera so that the user has a sense of less incongruity, or has a feeling of less unnaturalness.
In order to achieve the object of the present invention, according to a first aspect of the present invention, there is provided a camera comprising: a first lens group which performs focusing operation; a second lens group which moves relative to the first lens group to perform zooming operation; and a lens barrel which carries the first lens group and the second lens group, so that each of the first lens group and the second lens group can move along a zooming line including a plurality of focusing regions (focusing sections) and a plurality of zooming regions (zooming sections) in which a focusing region and a zooming region alternate with each other, wherein a feeding amount (forwarding amount) of the first lens group in one of the focusing regions is different from that of the first lens group in one of the others of the focusing regions.
The second aspect of the present invention provides a camera comprising: a first lens group which executes focusing operation; a second lens group which moves relative to the first lens group to execute zooming operation; and a lens barrel which carries the first lens group and the second lens group, so that each of the first lens group and the second lens group can move along a zooming line including a plurality of focusing regions (focusing sections) and a plurality of zooming regions (zooming sections) in which a focusing region and a zooming region alternate with each other, wherein a whole zooming area including the plurality of focusing regions and the plurality of zooming regions is divided into a plurality of zooming sub-areas, and wherein a feeding amount of the first lens group in one of the zooming sub-areas is different from that of the first lens group in one of the others of the zooming sub-areas.
In the zoom cameras provided by the first and second aspects of the present invention, the forwarding amount of the first lens group can be varied flexibly in whole zooming area, so that varying rates of the focal length and the view angle can be flexibly set.
The third aspect of the present invention provides a zoom camera comprising: a camera body; and a zoom lens barrel which is mounted on the camera body, wherein the zoom lens barrel comprises: a fixed barrel which is stationary relative to the camera body; a rotatable barrel which is connected to the fixed barrel via a helicoid and which is linearly fed relative to the fixed barrel with its rotating relative to the fixed barrel in a whole zooming area; and a plurality of lens groups that include a focusing lens group, each of which moves along a zooming line including a plurality of focusing sections and a plurality of zooming sections in which a focusing section and a zooming section alternate with each other, and that move in a direction of an optical axis relative to the rotatable barrel with their changing relative position when the rotatable barrel is forwarded, wherein, in each of the focusing sections, the focusing lens group is linearly fed relative to a rotational angle of the rotatable barrel, wherein the whole zooming area including the focusing sections and the zooming sections is divided into a wideangle-side zooming sub-area and a telephoto-side zooming sub-area, wherein, in the focusing sections which belong to one of the wideangle-side zooming sub-area and the telephoto-side zooming sub-area, the forwarding amounts of the focusing lens group relative to the rotational angle of the rotatable barrel in the focusing sections are equal to each other, and the forwarding amounts of the focusing lens group relative to the rotational angle of the rotatable barrel in the wideangle-side zooming sub-area and in the telephoto-side zooming sub-area are different from each other, wherein, in the wideangle-side zooming sub-area, the focusing lens group does not move relative to the rotatable barrel, and wherein, in the telephoto-side zooming sub-area, a helicoid formed on a carrying frame for the focusing lens group and a helicoid formed on the rotational barrel cooperates with each other, so that the focusing lens group is linearly fed relative to the rotational barrel.
In the zoom cameras provided by the third aspect of the present invention, the xe2x80x9cforwarding amount of the focusing lens group in the telephoto side zooming sub-areaxe2x80x9d can be made larger than that in the wideangle side zooming sub-area, so that the varying rates of the focal length and the view angle can be made linear in view of the user""s feelings in whole zooming area.